The invention concerns a multi-layer body with a micro-lens arrangement, which can preferably be used as an optical security element.
Optical security elements are used in window banknotes, ID cards, passports and similar security documents in order to be able to check the authenticity of those documents using simple means and to make it more difficult to forge those documents.
Solutions for optical security elements which provide micro-lenses for producing optical effects are known.
WO 03/061983 A1 describes an optical security element having a surface structure which has a plurality of micro-optical structures arranged in a specific pattern. The micro-optical structures are for example cylindrical lenses which co-operate with light-collecting structures and thus assemble micro-images arranged over a surface in the eye of a viewing person to provide a stereo image.
EP 0 698 256 B2 describes an optical security element which has a regular two-dimensional arrangement consisting of spherical micro-lenses, which is arranged over a regular arrangement of substantially identical printed micro-images, the size and the number of the images which can be perceived depending on how precisely the micro-images and micro-lenses are oriented relative to each other. In the case of exact orientation, it is possible to perceive an image of maximum size, while with increasing deviation the number of images increases and the image size decreases. Design configurations for example provide for the production of stereo images.
US No 2002/0012447 A1 describes a process and an apparatus in which inter alia micro-lens arrangements laid over geometrical structures produce characteristic moiré patterns. It is provided that the moiré patterns produced in that way are used for authenticity checking, by carrying out a comparison with a reference pattern.
EP 1 238 373 B1 describes a process and an apparatus for producing a characteristic moiré intensity profile by the superpositioning of a master screen and a basic screen. The master screen can be a micro-lens arrangement. It is provided that authenticity checking is effected by comparing the moiré intensity profile with a pre-stored moiré intensity profile.